scholarly journals Geophysical Survey of the Hillfort Staré Zámky near Brno-Líšeň, Czech Republic

2020 ◽  
Vol XI (2) ◽  
pp. 183-195
Author(s):  
Peter Milo ◽  
◽  
Tomáš Tencer ◽  
Michal Vágner ◽  
Michaela Prišťáková ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Czech Republic ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Magnetic Survey ◽  
Archaeological Research ◽  
Structural Elements ◽  
Geophysical Research ◽  
Resistivity Tomography ◽  
Geophysical Surveys

The aim of this paper is to present the results of geophysical surveys at the Staré zámky site near Brno-Líšeň, which were carried out in 2019. Electrical resistivity tomography, georadar survey and large-scale magnetic prospection were all carried out there. The primary task of the first two methods was to investigate the inner structure of the still-existing ramparts and to identify their individual structural elements. The magnetic survey focused on the identification of areas where potential archaeological features can be found – together with the identification of previously-unknown fortifications. The surveys were successful: we have found numerous settlement features from different phases of settlement, an early medieval cemetery and fortifications of various types, sizes and state of preservation. The results of previous archaeological research of the site played an important role for interpretation of the geophysical data. Together these results provide important insights into the study of the complex fortified settlement of Staré zámky. Despite our results, some questions which cannot be answered by geophysical research alone remain unanswered.

Results of Geophysical Research at the Ust`-Biyke-I Site (in the Altai)

2021 ◽  
Vol 33 (1) ◽  
pp. 73-84
Author(s):  
Olenchenko V. ◽  
◽  
Shnaider S. ◽  
Osipova P. ◽  
Kalganov A. ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Bronze Age ◽  
Electrical Resistivity Tomography ◽  
Ground Surface ◽  
Basic Research ◽  
Archaeological Site ◽  
Anthropogenic Activity ◽  
Geophysical Research ◽  
Resistivity Tomography ◽  
Geophysical Surveys

Abstract: Ust’-Biyke-I may become one of the most important archaeological complexes in the northern Altai region. Previous research established that the site was first occupied in the developed Mesolithic. Traces of subsequent occupations up to the Bronze Age were later discovered, in addition to burial structures. A loss of archaeological deposits at the mouth of the Biyke River occurred due to natural and anthropogenic activity. In order to identify the most promising areas for future excavations, geophysical surveys of the site were conducted. An area of 31.5 x 24 m was examined with electrical resistivity tomography (ERT) and ground-penetrating radar (GPR). Results revealed an object with a diameter of about 4 m that was not visible on the ground surface. In its center at a depth of 1.5 m, a local anomaly was observed. Another isometric anomaly was observed in the southwestern part at a depth of 0.75 m. Other anomalies were also noted in the surveyed area, some of which are visible in the modern terrain as small depressions. Future excavations will clarify the geophysical survey. Keywords: Altai, archaeological site, geophysical research, electrical resistivity tomography, groundpenetrating radar, settlement Acknowledgements: Geophysical study at the site was conducted with the financial support of the Russian Foundation for Basic Research (Project № 17–29–04122), archaeological work was carried out at the expense of the project NGS-67706R-20.

Dense 3D electrical resistivity tomography to understand complex deep landslide structures

2021 ◽  
Author(s):  
Julien Gance ◽  
Orlando Leite ◽  
Myriam Lajaunie ◽  
Kusnahadi Susanto ◽  
Catherine Truffert ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Surface Deformation ◽  
Reference Model ◽  
Slope Instability ◽  
Complex Objects ◽  
Alluvial Deposits ◽  
Resistivity Tomography ◽  
The Village

<p>Large scale slope instabilities are complex objects controlled by multiple parameters. The underground and superficial structure of the slope plays a major role as it often controls water circulations, potentially causing weathering and damaging processes, and permits the local storage of water masses, causing temporary overload. In addition, the structure of the subsurface often delineates rock-volumes with variable mechanical properties, whose spatial distribution greatly influences the behavior of the slope. This work illustrates how Dense 3D Electrical Resistivity Tomography can provide relevant constraints on these parameters.</p><p>The village of Viella, in France (Hautes-Pyrénées), is affected by strong slope movement since 2018, when a massive rockslide above the village modified the stress conditions of the entire slope and, potentially, the hydrogeological context. As a consequence, some houses and infrastructures are progressively damaged, leading to heavy measures (houses evacuation). This complex, deep-seated (> 80 m), slope instability covers an area of ca. 650 000 m², is primarily composed of altered shists, colluviums, and non-consolidated alluvial deposits, forming several kinematic units with surface velocities in the range [0.5 – 5] mm.month<sup>-1</sup>.</p><p> </p><p>A 3D dense electrical resistivity tomography was realized using the FullWaver system, to characterize the structure and the forcing factors of this unstable slope. 55 V-FullWavers receivers (3 -electrodes, 2 channels sensors) were quasi-evenly distributed over a surface area of 400 x 500 m² with an interval of 90 m, apart from the village area, where no electrode could be grounded. Each V-FullWaver recorded signals through two orthogonal dipoles of 25 m length. Current injections were realized with a high-power transmitter (6 kW, 16 A, 3000 V). 235 injection dipoles were used. The system injected current between a fixed remote electrode (more than 1 km away from the site to increase the investigation depth) and a local mobile electrode, moved all over the investigated area in between the V-Fullwaver receivers, with an interval of approximately 40 m, except in the village area.</p><p> </p><p>The resulting 3D resistivity model presents a high spatial variability until 100 to 150 m depth approximately, that highly relates to the complex strain dynamics of the slope and the hydrogeological observations. It highlights the relation between the most active kinematic compartments and the large-scale structure of the slope.</p><p>It provides a first understanding of the role of local compacted rocks in the buildup of surface deformation but also on the localization of heterogeneities (fissures, scarps) which may relate to water circulation paths.</p><p>. This 3D image of the slope is the first structural reference model for future hydrogeological and geomechanical studies aiming at deducing the possible evolution of the slope.</p>

scholarly journals Large-scale electrical resistivity tomography in the Cheb Basin (Eger Rift) at an International Continental Drilling Program (ICDP) monitoring site to image fluid-related structures

Solid Earth ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 1951-1969 ◽  
Author(s):  
Tobias Nickschick ◽  
Christina Flechsig ◽  
Jan Mrlina ◽  
Frank Oppermann ◽  
Felix Löbig ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Fault Zone ◽  
Large Scale ◽  
Monitoring Site ◽  
Earthquake Activity ◽  
Resistivity Tomography ◽  
Scientific Drilling ◽  
Eger Rift ◽  
Geophysical Surveys ◽  
Cheb Basin

Abstract. The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N–S-striking Počatky–Plesná fault zone (PPZ) and the NW–SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are one of the subjects of the International Continental Scientific Drilling Program (ICDP) project “Drilling the Eger Rift” in which several geophysical surveys are currently being carried out in this area to image the topmost hundreds of meters to assess the structural situation, as existing boreholes are not sufficiently deep to characterize it. As electrical resistivity is a sensitive parameter to the presence of conductive rock fractions as liquid fluids, clay minerals, and also metallic components, a large-scale dipole–dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used permanently placed data loggers for voltage measurements in conjunction with moving high-power current sources to generate sufficiently strong signals that could be detected all along the 6.5 km long profile with 100 and 150 m dipole spacings. After extensive processing of time series for voltage and current using a selective stacking approach, the pseudo-section is inverted, which results in a resistivity model that allows for reliable interpretations depths of up than 1000 m. The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but it also shows a very conductive basement of phyllites and granites that can be attributed to high salinity or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for CO2 ascent are not observed with this kind of setup, which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity and GPS data along this profile in order to constrain ERT results. A gravity anomaly of ca. −9 mGal marks the deepest part of the Cheb Basin where the ERT profile indicates a large accumulation of conductive rocks, indicating a very deep weathering or alteration of the phyllitic basement due to the ascent of magmatic fluids such as CO2. We propose a conceptual model in which certain lithologic layers act as caps for the ascending fluids based on stratigraphic records and our results from this experiment, providing a basis for future drillings in the area aimed at studying and monitoring fluids.

scholarly journals Experimental Studies on the Changes in Resistivity and Its Anisotropy Using Electrical Resistivity Tomography

2012 ◽  
Vol 2012 ◽  
pp. 1-10
Author(s):  
Tao Zhu ◽  
Jian-Guo Zhou ◽  
Jin-Qi Hao
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Experimental Studies ◽  
Major Axis ◽  
Residual Resistivity ◽  
Resistivity Tomography ◽  
D Region ◽  
Resistivity Anisotropy

Three measuring lines were arranged on one of free planes of magnetite cuboid samples. Apparent resistivity data were acquired by MIR-2007 resistivity meter when samples were under uniaxial compression of servocontrol YAW-5000F loadingmachine in laboratory. Then we constructed the residual resistivity images using electrical resistivity tomography (ERT) and plotted the diagrams of apparent resistivity anisotropy coefficient (ARAC)λ∗and the included angleαbetween the major axis of apparent resistivity anisotropy ellipse and the axis of load with pressure and effective depth. Our results show that with increasing pressure, resistivity and the decreased (D region) and increased (I region) resistivity regions have complex behaviors, but when pressure is higher than a certain value, the average resistivity decrease and the area of D region expand gradually in all time with the increase of pressure, which may be significant to the monitoring and prediction of earthquake, volcanic activities, and large-scale geologic motions. The effects of pressure onλ∗andαare not very outstanding for dry magnetite samples.

scholarly journals Exploring the regolith with electrical resistivity tomography in largescale surveys: electrode spacing related issues and possibility

2020 ◽  
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the Critical Zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical Resistivity Tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, smaller ES – albeit offering poorer shallow apparent resistivity data – are often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic conductive/resistive/conductive three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

scholarly journals A review of open software resources in python for electrical resistivity modelling

2022 ◽  
Vol 9 (1) ◽  
Author(s):  
Yonatan Garkebo Doyoro ◽  
Ping-Yu Chang ◽  
Jordi Mahardika Puntu ◽  
Ding-Jiun Lin ◽  
Tran Van Huu ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Geophysical Research ◽  
Resistivity Tomography ◽  
Subsurface Structures ◽  
Data Inversion ◽  
Scripting Language ◽  
And Inversion ◽  
Geoelectric Data ◽  
Insight Into

AbstractGeophysical modelling performs to obtain subsurface structures in agreement with measured data. Freeware algorithms for geoelectrical data inversion have not been widely used in geophysical communities; however, different open-source modelling/inversion algorithms were developed in recent years. In this study, we review the structures and applications of openly Python-based inversion packages, such as pyGIMLi (Python Library for Inversion and Modelling in Geophysics), BERT (Boundless Electrical Resistivity Tomography), ResIPy (Resistivity and Induced Polarization with Python), pyres (Python wrapper for electrical resistivity modelling), and SimPEG (Simulation and Parameter Estimation in Geophysics). In addition, we examine the recovering ability of pyGIMLi, BERT, ResIPy, and SimPEG freeware through inversion of the same synthetic model forward responses. A versatile pyGIMLi freeware is highly suitable for various geophysical data inversion. The SimPEG framework is developed to allow the user to explore, experiment with, and iterate over multiple approaches to the inverse problem. In contrast, BERT, pyres, and ResIPy are exclusively designed for geoelectric data inversion. BERT and pyGIMLi codes can be easily modified for the intended applications. Both pyres and ResIPy use the same mesh designs and inversion algorithms, but pyres uses scripting language, while ResIPy uses a graphical user interface (GUI) that removes the need for text inputs. Our numerical modelling shows that all the tested inversion freeware could be effective for relatively larger targets. pyGIMLi and BERT could also obtain reasonable model resolutions and anomaly accuracies for small-sized subsurface structures. Based on the heterogeneous layered model and experimental target scenario results, the geoelectrical data inversion could be more effective in pyGIMLi, BERT, and SimPEG freeware packages. Moreover, this study can provide insight into implementing suitable inversion freeware for reproducible geophysical research, mainly for geoelectrical modelling.

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